The open source community is participating in this race to the cloud in two key ways. First, much open source software, particularly software for enterprises and small businesses, is now available on a SaaS basis. This provides customers with quality, low-cost applications and eliminates the hassles of deploying software on their own servers. At the same time, it gives open source companies a viable business model that allows them to make money from their technology.

Second, many open source projects are focusing on developing the infrastructure and management software that makes cloud computing possible. These tools are used by public cloud computing providers and by organizations that want to set up private or hybrid clouds.

For this list, we've collected some of the best of both types of open source cloud apps. Although there are a few projects here that are aimed at home users, most of these are applications suitable for businesses.

Cloud Infrastructure and Management

Numerous technology companies have announced their support for OpenStack, making it the leading open source cloud computing platform. It allows data centers to pool their compute, storage, and networking resources and manage them through a dashboard interface. Operating System: OS Independent.

This Apache project offers a turnkey Infrastructure as a Service (IaaS) solution. It's used both by public cloud computing vendors and by organizations running their own private clouds. Operating System: OS Independent

This project aims to simplify the process of setting up and running private or hybrid cloud environments. The project is completely open source, but services and support are available thorough C12G Labs, which manages the project. Operating System: Linux.

Short for "Elastic Utility Computing Architecture, Linking Your Programs To Useful Systems," Eucalyptus allows organizations to build private or hybrid cloud environments that are compatible with Amazon Web Services. Support is available on a subscription basis. Operating System: Linux.

Synnefo is a complete cloud infrastructure stack built using Google Ganetti, OpenStack and KVM. There's a demo on the website, so you can see the dashboard in action before you download. Operating System: Linux.

Used by companies like GE, Expedia, Samsung, Oracle, Disney, Nokia, CBS and Accenture, Scalr is an enterprise-class cloud management solution. In addition to the open source version, it also comes in paid hosted or on-premise versions. Operating System: Linux.

This enterprise-class tool combines datacenter management/system administration and IaaS provisioning into a single tool. It comes in both a free community version and a paid enterprise version. Operating System: Linux.

Sponsored by Dell, Desein describes itself as a "Open Source cloud abstraction library for Java." It's a model for IaaS and PaaS offerings that enables applications to run in any cloud environment. Operating System: Linux.

Cloud Desktop

Although it is now commercial software available from IBM and other partners, you can still access the older, open source versions of this cloud desktop solution from the SourceForge link above. It claims to be the first and the most popular open source cloud desktop. Operating System: Linux.

A community group is continuing development of the open source version of eyeOS, which they have forked under the name Oneye. It's currently in version 0.9, and only community support is available. Operating System: Linux.

As you can probably guess from the name, this project allows individual users to set up their own personal cloud so they can access their files, email, and multimedia content from any device. If you don't have your own server, the website links to several service providers who offer hosting. Operating System: Windows, Linux.

Hypervisors

Sponsored by the Linux Foundation, Xen has been incorporated into numerous other open source projects, including Eucalyptus, Apache CloudStack, OpenNebula and OpenStack. Amazon began using it for its cloud computing service in 2006, and it also runs many other public clouds. Operating System: OS Independent.

Platform as a Service

Owned by RedHat, OpenShift is both downloadable software that allows organizations to set up their own PaaS and an online public PaaS. It supports technologies like Java, PHP, Ruby, Node.js, Python, Perl, MySQL, MongoDB, PostgreSQL and Jenkins. Operating System: Linux.

Now owned by Pivotal, Cloud Foundry counts Verizon, SAP and Baidu among its users. In addition to sponsoring the open source project, Pivotal also offers Pivotal Web Services, a public PaaS based on Cloud Foundry, and Pivotal CF, a supported version of Cloud Foundry that enterprises can use to set up a private PaaS. Operating System: Linux.

Backup

Amanda, short for "Advanced Maryland Automatic Network Disk Archiver," claims to be the "most popular open source backup and recovery software in the world." Zmanda, which sponsors development of the tool, offers cloud-based backup based on the same software. Operating System: Windows.

Designed for enterprise use, Bacula also lays claim to the "most popular" title. Bacula Systems offers paid support and services, including "Bacula for the Cloud." Operating System: Windows, Linux, OS X.

Big Data Tools

Hadoop allows organizations to process large data sets quickly across clusters of distributed systems, as in cloud computing environments. It's used by many of the biggest names on the Web, including Adobe, AOL, Alibaba, Ebay, Facebook, FOX, Google, Hulu, LinkedIn, The New York Times, Spotify, StumbleUpon, Twitter and Yahoo. Operating System: Windows, Linux, OS X.

Business Intelligence

Recently acquired by TIBCO, Jaspersoft offers both paid and free open source versions of its highly popular analytics software. Its cloud analytics service starts at just $1/hour. Operating System: OS Independent.

OpenI strives to help enterprises go from "data to insights in 72 hours with open source." It's a reporting tool that integrates with other open source BI solutions and can be deployed to Amazon Web Services very easily. Operating System: OS Independent.

Business Process Management

This award-winning open source business process management tool counts Toyota and Lenovo among its users. In addition to on-premise versions, it comes in a cloud version with several different pricing tiers. Operating System: Windows, Linux.

Content Management

Like Microsoft SharePoint, Alfresco offers collaboration, document management and media management capabilities. The link above will take you to the paid cloud version, and it also comes in both free and paid on-premise versions. Operating System: Windows, Linux, OS X.

This project allows enterprises to set up self-service and knowledge-base websites where their customers can quickly find information they need. The cloud-based version is now the primary version of the software, but you can still download the open source MindTouch Core from SourceForge. Operating System: Windows, Linux.

Customer Relationship Management (CRM)

SugarCRM boasts millions of users at companies around the world. The cloud-based paid version has three different pricing tiers, or you can download the community version for free. Operating System: Windows, Linux, OS X.

Downloaded more than three million times, vTiger boasts a low total cost of ownership, whether you use the paid cloud-based version or the free open source download. It includes email marketing, project management, calendar, task management, document management, inventory management, reporting and other capabilities. Operating System: Windows, Linux, iOS, Android.

While most CRM tools are built with for-profit companies in mind, Orange Leap was made for non-profits. The link above has plenty of information about the paid, cloud-based version, but you can also download the open source version from GitHub. Operating System: Windows.

The latest features in this CRM package include Twilio and Twitter integration, undelete, an HTML5 calendar and more. It's available in three editions—community (free and open source), professional and enterprise—all of which can be accessed in the cloud or deployed on premise. Operating System: Windows.

Database

This distributed database offers high availability, fault tolerance, operational simplicity and scalability. In addition to the open source version, it comes in a supported enterprise version and a Cloud Storage (CS) version that is ideal for cloud computing environments. Operating System: Linux, OS X

Document Management Systems (DMS)

Web-based OpenKM is a full-featured document management system with version control and file history, metadata, scanning, workflow, search and similar capabilities. It comes in three versions: the free open source edition, the supported professional version and the subscription-based cloud version. Operating System: OS Independent.

LogicalDOC is a cross-platform document management system that aims to make the paperless office a reality. It's available in community, business and enterprise editions, and the enterprise version can also be purchased on an SaaS basis. Operating System: OS Independent.

Designed to comply with ISO 17025 and OIE standards for document management, OpenDocMan offers features like easy setup, robust user management, change tracking, search, robust security and support for multiple languages. In addition to the free download, it's also available as a hosted service, and cloud-based backup can be purchased for an additional fee. Operating System: OS Independent.

E-Commerce

Used by more than 200,000 online store's, eBay's Magento platform counts Vizio, Homedics, The North Face, Office Max and many small businesses among its users. "Magento Go" is the name for its hosted solution, which is free for 30 days and starts at just $15 per month. Operating System: Windows, Linux, OS X.

E-mail/Collaboration/Groupware

Basecamp users will find this cloud-based project management system very familiar. Organizations can host it on their own servers or subscribe to the hosted service, which has three pricing tiers: freelancer, studio and enterprise. Operating System: OS Independent.

This enterprise-class groupware and CRM solution comes in a free community version or a paid professional version that adds helpdesk, time tracking, mobile sync, project management and document editing. Cloud-based hosting starts at 10 euros per month and guarantees 99.99% uptime. Operating System: OS Independent.

Used by companies like Comcast, Dell, Rackspace, Red Hat, Mozilla, Titleist and H&R Block, Zimbra is an email, calendar, address book and file sharing solution that is similar to Microsoft Exchange/Outlook. According to the website, it was "built for the cloud, both public and private." Operating System: Linux, Unix, OS X.

Cyn.in describes itself as "the first open source collaborative knowledge management appliance." It's available three ways: as a free community download, as a paid on-premise appliance or on an on-demand SaaS basis. Operating System: Windows, Linux, OS X.

Used by more than 1 million people in 150 different countries, Feng Office offers project management, billing, document management, messaging and scheduling capabilities. Feng Sky is the name for the paid, cloud-based version, and Feng Onsite is the self-hosted version, which comes in both free and paid versions. Operating System: Windows, Linux, OS X.

Egroupware's website boasts that it is "the leading online collaboration tool and the top choice for big enterprises, small businesses and teams within and across organizations all over the globe." It offers both community and enterprise editions, as well as paid hosting with several different pricing tiers. Operating System: OS Independent.

TeamLab combines document editing, mail, CRM and project management into a single package. Download the open source version, pay for a supported enterprise version, or use the hosted cloud version. Unlike most other projects, TeamLab also offers a free cloud version for non-profits. Operating System: OS Independent.

E-mail Marketing

Downloaded more than 450,000 times, OpenEMM claims to be the "first open source application for e-mail marketing." See the link above for the open source version, or visit the Agnitas website for information on commercial support and eMM-Xpress, the cloud-based version of the same software. Operating System: Windows, Linux.

According to its website, phpList is "the world's most popular open source email campaign manager." In addition to the free download, it comes in a hosted version with fees based on the number of messages sent or the number of subscribers. Operating System: OS Independent.

Enterprise Resource Planning (ERP)

Formerly known as Open ERP, Odoo boasts more than 2 million users, including Danone, Canonical and Singer. It includes more than 3,000 individual apps that work together to help people manage their businesses. A free open source download is available, but it's primarily sold on a SaaS basis. Operating System: Windows, Linux.

Award-winning Openbravo offers open source ecommerce and ERP solutions. The supported commercial versions are sold through third-party partners, but the company also offers a free download and hosted on-demand versions. Operating System: OS Independent.

The self-proclaimed "world's #1 open source ERP," xTuple includes tools for accounting, time & expense, CRM, sales, purchasing, manufacturing, inventory and distribution. Postbooks is the free open source version, but it comes in many other versions which can be download or used in the cloud. Operating System: Windows, Linux, OS X.

Compiere claims to be "the most modern, adaptable and affordable ERP solution." It comes in community and enterprise editions, and while it isn't available in a SaaS version, it can be easily deployed to Amazon Web Services. Operating System: Windows, Linux, OS X.

This application includes both ERP and CRM functionality, plus ecommerce, business intelligence and more. In addition to the open source version, there's also a paid professional version, and the company also has an easy-to-deploy Amazon Machine Image (AMI) that allows paid license holders to get Opentaps up and running on Amazon's cloud in just minutes. Operating System: Windows, Linux.

Human Resource Management (HRM)

Used by Lufthansa, Sandals, Red Hat, Stanley Black & Decker and many other companies, OrangeHRM calls itself "the world's most popular HR software." It comes in open source, professional or enterprise versions, and all three can be deployed via OrangeHRM Live, a hosting service powered by Rackspace. Operating System: Windows, Linux, OS X.

WaypointHR software is available as an open source download or in a cloud version, which offers additional features. It places the emphasis on security and ease of use while tracking employee demographic information and employment records. Operating System: OS Independent.

Invoicing

SimpleInvoices describes itself as "free web based invoicing developed by the community, for the community." You can run it on a standalone Windows PC, set it up on your own Web server or use hosting services provided by a third party partner. Operating System: OS Independent.

Project Management

Onepoint combines both project management (PM) and project portfolio management (PPM) capabilities into a single package. It comes in many different commercial and open source versions, including some cloud editions. Operating System: Windows, Linux, OS X.

School Management/Learning Management Systems

Designed for educational institutions of all sizes, this student information system tracks demographics, grades, report cards, attendance and much more. It comes in community (free), school (paid) and district (paid) versions, and cloud-based hosting is also available. Operating System: OS Independent.

Instructure's Canvas learning management system aims to make it easier to implement distance learning or 1:1 learning initiatives in K-12 or higher education. The main website (link above) offers information on the commercial and cloud versions; the easiest way to get the open source version is from GitHub. Operating System: Linux, Unix, OS X.

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